The present invention relates generally to a washer system particularly suited for automotive vehicles and more particularly, to a method and an apparatus for purging at least a portion of the washer system.
Currently, most washer liquids contain volatile organic compounds (VOCs), such as alcohols or glycols, to depress the overall washer liquid freezing point temperature. The most common washer liquid is a solution of methyl alcohol (methanol) by weight in demineralized water, including a small amount of detergent and dye.
After having been dispensed onto the vehicle surface to be cleaned, the volatile organic compounds contained in the washer liquid can evaporate into the atmosphere. With sufficient atmospheric warmth and sunlight, such as during a hot and sunny day, certain VOCs, including those used as freezing point depression agents in washer liquid, may participate in a complex series of photochemical reactions in the atmosphere leading to the formation of ozone, a major component of smog (air pollution). For this reason, many governments have placed limits on total allowable vehicular VOC emissions, primarily with respect to engine exhaust and fuel delivery systems. As regulations become increasingly restrictive, VOC emissions from washer systems may be counted against total vehicular VOC emissions, though this currently is not the case.
Although reduction of VOC emissions is not addressed, U.S. Pat. No. 5,261,254 uses water extracted from the air in its washer system. The ""254 patent is a windshield washer system that contains three separate reservoirs. One reservoir is used to collect water from the air. Another reservoir is used to hold an anti-freeze solution. Finally, the third reservoir is used to combine the water extracted from the air with the anti-freeze solution creating a freeze-resistant washer liquid.
U.S. Pat. No 5,946,763 is a windshield washer system that also contains three reservoirs, although the reduction of VOC emissions is again not addressed. One reservoir contains collected rainwater. A second reservoir contains anti-freeze solution. A third reservoir contains a strong cleaning agent. According to the level of freeze protection needed, the anti-freeze solution is pumped into the tank holding the rainwater to create a washer liquid that is freeze-resistant. The ""763 patent describes a method of mixing the rainwater with the anti-freeze upon determining the outside temperature, the washer liquid temperature, and the density of the washer liquid. Both the ""763 and ""254 patents transfer liquids from one reservoir to another and to the spray nozzles via a pump, a pump in combination with tubing, or via gravity. Both patents provide a single reservoir and pump assembly that is used to hold and distribute the washer liquid to the vehicle surface to be cleaned. In addition, both patents describe situations when water will be distributed throughout various reservoirs, pumps, tubing, passages and nozzles. When the temperature drops below the freezing point of water (0xc2x0 C.), some of these components may freeze shut, thereby disabling the washer systems. Although the ""763 patent describes a method of creating an ideal freezing point solution, it uses signals from several sensors in determining when to add anti-freeze to the washer liquid. The ""763 patent uses a sensor to measure temperature of the washer liquid, a sensor for measuring the outside temperature, and a sensor for measuring the density of the washer liquid. The use of three sensors and various other components causes the ""763 patent to be relatively complex and costly to produce.
Disadvantages associated with the systems disclosed in the ""763 and ""254 patents include freezing in the portion of the washer system that distributes washer liquid, when the washer liquid therein has a freezing point greater than or equal to the surrounding temperature. In addition, since only one washer liquid reservoir and pump assembly is provided, once the water is mixed with the anti-freeze solution to form the washer liquid, the only washer liquid option available is a freeze-resistant mixture. When outside temperatures transition to a level where ozone formation is possible, such as from a cold day or region to a hot day or region, the freeze-resistant mixture is still used, thereby emitting VOCs that are known contributors to ozone and smog formation.
It would therefore be desirable to provide a washer system that dispenses a washer liquid that emits a reduced amount of VOCs over conventional washer systems and that does not become inoperative due to freezing of the washer liquid.
One object of the invention is to reduce the amount of VOC emissions from the washer system of an automotive vehicle. Another object of the invention is to provide a washer system that purges at least a portion of the fluid distribution circuit of the washer system before there is a chance of freezing.
In one aspect of the invention, a washer system includes a first reservoir containing a washer liquid that may freeze at or below 0xc2x0 C., such as a solution of soap and water, a second reservoir containing a freeze-resistant washer liquid, such as a solution of water, alcohol and soap, and an exit circuit. The first reservoir, second reservoir, and exit circuit are fluidically coupled to a fluid distribution circuit. A fluid purge apparatus is also fluidically coupled to the fluid distribution circuit. An electronic control module (ECM) is electrically coupled to the fluid distribution circuit, the fluid purge apparatus, and a temperature sensor. The ECM controlling the fluid purge apparatus purges at least a portion of the fluid distribution circuit and the exit circuit upon receiving a temperature signal from the temperature sensor indicative of a potential for freezing. The fluid purge apparatus is used to prevent freezing, in the portion of the washer system that distributes fluid, when the temperatures are low enough to cause freezing.
Another aspect of the invention contemplates a method of operating a washer system having a first reservoir containing a freezable washer liquid, a second reservoir containing a freeze-resistant washer liquid, and a fluid purge apparatus. The ECM determines a temperature and purges the fluid from at least a portion of a fluid distribution circuit and an exit circuit in response to the temperature.
One embodiment of the present invention permits freezing of the freezable washer liquid and use of the freeze-resistant washer liquid only during temperatures below a predetermined temperature. In addition, taking into consideration space constraints, at least a portion of this embodiment may be incorporated into a fan shroud assembly.
One advantage of the invention is that the washer system reduces the amount of emitted VOCs over prior known systems while preventing the system from being disabled by freezing temperatures.
The present invention itself, together with further objects and attendant advantages, is best understood by reference to the following detailed description, taken in conjunction with the accompanying drawings.